Molecular Psychiatry (2019): Towards precision medicine for pain: diagnostic biomarkers and repurposed drugs

[Ravn]

An objective biomarker - gene expression patterns - for pain? Can this be true?

https://www.nature.com/articles/s41380-018-0345-5 (A.B Niculescu et al.) Full text.

Abstract
We endeavored to identify objective blood biomarkers for pain, a subjective sensation with a biological basis, using a stepwise discovery, prioritization, validation, and testing in independent cohorts design. We studied psychiatric patients, a high risk group for co-morbid pain disorders and increased perception of pain.

The cohorts and the scientists are psychiatric patients/psychiatrists but otherwise the study seems to lean more biomedical - not a single mention of CBT - and recognition of different types of pain other than Central Sensitisation.

Pain is a subjective feeling with objective roots and profound evolutionary biological utility. It reflects perceived or actual damage to the organism
[...]
A phenotypic clustering analysis of the discovery cohort revealed two broad putative subtypes of High Pain states, a predominantly psychotic subtype, possibly related to mis-connectivity and increased perception of pain centrally, and a predominantly anxious subtype, possibly related to reactivity and increased physical health reasons for pain peripherally. Deeper analyses of the clustering in future studies may also substantiate further parsing of the subtypes, possibly into eight instead of only two subtypes, and of underlying differentiating biomarkers.

Finishes with a bit of hype though:

In conclusion, our work opens the door for precision medicine for pain, with objective diagnostics and targeted novel therapeutics. Given the massive negative impact of untreated pain on quality of life, the current lack of objective measures to determine appropriateness of treatment, and the severe addiction gateway potential of existing opioid-based pain medications, the importance of approaches such as ours cannot be overstated.

 

[rvallee]

We studied psychiatric patients

That's an odd choice considering you can barely whack around a pool noodle without hitting dozens of non-psychiatric chronic pain patients desperately willing to try anything to make the pain go away and ready to participate in research right now.

The study seems on the serious side but I strongly question motive when such an odd choice is made. That's as bad as including major depressive disorder and somatization patients in PACE, it just adds way too much distortion by choice, making interpretation more difficult than it should be.

Hammers just can't quit thinking about nails.

 

[Amw66]

That's an odd choice considering you can barely whack around a pool noodle without hitting dozens of non-psychiatric chronic pain patients desperately willing to try anything to make the pain go away and ready to participate in research right now.

The study seems on the serious side but I strongly question motive when such an odd choice is made. That's as bad as including major depressive disorder and somatization patients in PACE, it just adds way too much distortion by choice, making interpretation more difficult than it should be.

Hammers just can't quit thinking about nails.

Consent?

 

[Ravn]

The study seems on the serious side but I strongly question motive when such an odd choice is made. That's as bad as including major depressive disorder and somatization patients in PACE, it just adds way too much distortion by choice, making interpretation more difficult than it should be.

Going on memory here so could be wrong but I think it was a matter of convenience. They just happened to have these patients handy from another study or something along those lines, possibly even with some useful historical data available. (@Amw66 consent was discussed in the paper but can't recall the details now).

The authors discussed the matter that most of their patients had a merry mix of comorbidities, both psychological and physiological, and viewed that as a strength. They wanted a biomarker for pain that shows up no matter what underlying condition/s a patient is suffering from. Sensible enough provided all types of pain create the same gene expression pattern, or at least fit a small number of distinct gene expression patterns. They found at least 2 and possibly up to 8 subgroups. That's where I'm a bit dubious. Were their cohorts large enough to say something about that many subgroups with reasonable certainty?